Perfect solution

PUBLISHED : Sunday, 03 January, 1999, 12:00am
UPDATED : Sunday, 03 January, 1999, 12:00am

There is one solution to the growing mountain of recyclable paper in Hong Kong: compost it.

Composting is the breakdown (decay) of organic matter by soil micro-organisms into humus, the complex biological matter that is the essential factor of soil fertility.

This process can take years in the wild, but with modern methods it can be as short as a fortnight.

It can also be done on an industrial scale, and a growing number of cities around the world incorporate composting schemes with their refuse and environmental management.

The US military even composts some of its old TNT explosives.

The beauty of composting is that it solves a number of refuse problems at the same time and creates a new and very useful product.

It requires the following: carbon matter, nitrogen matter, moisture, soil micro-organisms, and oxygen in the quicker methods. It is low-tech, involving little more than making large piles that need to be turned and aerated occasionally. And although some of the raw inputs may not be particularly inviting, a well-made and maintained compost pile does not stink and the end product is very clean, with a pleasant, earthy odour.

Carbon matter is best provided by dried plants: leaves, straw, grass cuttings etc. Nitrogen matter comes from fresh plants and animal waste such as manure, blood, feathers, fish trimmings, etc.

Manure and soil provide micro-organisms. Oxygen is provided by turning the pile occasionally.

If the materials are in the right proportion the moisture content will also be about right.

The optimum carbon to nitrogen ratio is about 30:1, so carbon matter provides the bulk of compost pile. After dry plants (which contain many other nutrients), a good source of carbon is uncoated paper, especially newsprint as it breaks down quickly.

Most inks are not too much of a problem as they too are carbon based. Coated glossy papers contain other materials that might not break down readily and would need separate treatment.

For nitrogen matter, Hong Kong's wet markets are excellent sources of plant and animal waste, which at present just clog up our landfills.

Prunings and grass cuttings from parks and roadsides are also fine, as long as they are not contaminated with pesticides or herbicides.

Another interesting by-product of composting is heat - the interior of a good pile of one cubic metre can reach 70 degrees Celsius at the peak of the process.

Engineers in other countries are examining ways of harnessing this, such as supplementing household hot water systems.

Methane gas is another by-product.

The Government's Waste Reduction Framework Plan aims to reduce Hong Kong's rubbish piles. The materials I have listed, constitute a very large percentage of our garbage.

At present it is dumped to rot in our landfills, performing no useful function other than generating noxious gases. Indeed, the term 'waste' is highly subjective, because the composter finds these materials very useful indeed.

Any good recycling programme must start at the source: the factory, the market, the school, the home. People must learn to separate their wastes at the point of disposal, with different receptacles for kitchen scraps, newsprint, plastic, glass and so on. It is not at all difficult and in some Japanese cities this type of recycling has full community backing.

Many cities around the world have good urban-scale composting schemes, and Hong Kong would do well to study some of them. But we also have great technical and logistical expertise and with a little imagination, environmental technology could become a Hong Kong specialty.

Waste disposal is a problem; recycling is an industry.